Study On The Degradation Rule Of Oxytetracycline In Wuhan Section Of The Yangtze River

The sediment concentration of rivers in China is relatively high during the wet season and the composition of suspended sediments is mainly viscous fine sediment.Due to its small specific gravity and large surface area,it easily adsorbs pollutants in natural water bodies,which affects the migration and transformation process of pollutants in the environment.Antibiotics are widely used in the treatment and prevention of human and animal diseases,and the ripening of animals and agricultural products.Antibiotics that have not been completely absorbed or decomposed enter the environment in the form of maternal or intermediate metabolites.Because of their hydrophilicity,they eventually enter the water environment.The intermediates produced by antibiotics during the conversion process may have stronger biological toxicity than the parent.The influence of sediment in natural water on the degradation behavior of antibiotics is still unclear.Therefore,research on the degradation rule of antibiotics under different water and sediment conditions has positive significance for promoting the development of theoretical research on environmental behavior of antibiotics.In this paper,oxytetracycline was selected as a representative antibiotic drug,and a series of studies were carried out on the degradation process and intermediate products of oxytetracycline in natural water.The main research results include the following aspects:(1)Comparing the detection results of oxytetracycline by high performance capillary electrophoresis and high performance liquid chromatography,and establishing a test method for rapid detection of oxytetracycline concentration in water.The results show that no need of special pretreatment is required for both them.Under optimized test conditions,oxytetracycline can be determined in 6 minutes by high performance liquid chromatography,which has better sensitivity and reproducibility.The linear range is 0.2-2 mg/L.(2)The degradation rules of oxytetracycline under different water and sediment had been analyzed and compared.In the sediment-bearing water,the adsorption process mainly occurred in the first 6 hours,and the degradation process generally occurred after 24 hours.The higher the concentration of sediment makes the faster adsorption rate and greater adsorption equilibrium of oxytetracycline.When the sediment content in water is changed between 50-100 mg/L,the effect on the degradation process is small.Under the same concentration condition,the smaller the particle size of suspended particles makes the faster adsorption rate,but the change of adsorption equilibrium is small.The degradation process of oxytetracycline in the water was consistent with the first-order kinetic reaction.(3)Under the shading condition indoor,oxytetracycline concentration did not change in almost 3 hours,which indicated that the hydrolysis of oxytetracycline did not occur in the initial stage of the reaction.Under natural light condition,the photodegradation process of oxytetracycline occurred fast and its half-life is only about 20 minutes.Under fluorescent lamp condition,the photodegradation rate of oxytetracycline is slower than that under natural light conditions,which may be related to the weaker daylighting light and the single type of light source.(4)The oxytetracycline-degrading strains which acclimated from the fish pond sediments with long-term application of antibiotics have a degradation efficiency of 39%.The addition of suspended particulates contributed to the biodegradation of oxytetracycline.The proliferation rate of the degrading bacteria is accelerated,and the degradation efficiency is also improved in natural waters containing suspended particulate matter.(5)The intermediate products of oxytetracycline degradation under different conditions were analyzed by high performance liquid chromatography coupled with triple quadrupole mass spectrometry.Eight major products were identified,and their m/z were 416.6?432.6?437.6?453.7?460.6?475.7?476.6 and 497.6 respectively.Due to the lack of standard products,the product could not be quantitatively analyzed.Therefore,the peak area was used as the reference of the product concentration,and the degradation process of oxytetracycline under different experimental conditions was determined according to the change of the amount of each product in different time periods.